Epitaxial V-groove bipolar integrated circuit process

A new four-mask "V-groove" process for the fabrication of bipolar integrated circuits has been developed. The process utilizes epitaxial ν/n⁺/n^-layers and anisotropic etching oflangle100ranglesilicon to eliminate the buried layer and isolation diffusions as well as the need for masking the base diffusion of the standard six-mask bipolar integrated circuit process, n-p-n transistor, resistor, and Schottky diode characteristics are equivalent to or exceed those of the standard process. A five-mask V-groove process provides improved lateral p-n-p transistors compared with the four-mask approach. The V-groove integrated circuit structure offers simpler processing, smaller isolation capacitances, lower parasitic collector resistances, larger packing densities, and higher junction breakdown voltages than standard bipolar integrated circuits without degradation of other properties.     

Thermocompression bonding of external package leads on integrated circuit substrates

A new technique for attaching external package leads to metallized substrates is presented. Gold-plated copper lead frames and gold-plated headed leads of various compositions are thermocompression bonded to metallized alumina substrates. The generated patterns on the substrates consist of an evaporated layer of gold over an evaporated layer of titanium. The leads are bonded simultaneously to form gold diffusion bonds between the leads and the metallized substrate. The lead frames are stamped from 0.005 inch and 0.010 inch thick copper. The headed leads range in size from 0.017 inch in diameter to 0.025 inch square. The various problems encountered in the development of this technique and their related solutions will be discussed. The bonding tool consists of a base for positioning the substrate and a bonding tip which applies the necessary pressure and temperature to produce a bond. The base and bonding tip for lead frames can compensate for camber and nonuniform thickness in the ceramic while the base and bonding tip for headed leads are noncompensating. The various parameters of bonding time, bonding temperature, bonding force, and bond strengths will be presented. In addition, hermetic seal evaluations will be discussed. A comparative cost analysis will be made between attaching leads individually by welding versus attaching all package leads simultaneously by the thermocompression bonding technique. This investigation has opened additional avenues toward determining the full scope and capability of thermocompression bonding in an area previously dominated by brazing and the sealing of metal to glass and/or ceramics.     

Neural net analysis of integrated circuit yield dependence on CMOS process control parameters

In this practical case study the method of self-organizing map (SOM) neural net is applied to analyze a CMOS process problem, where the device under study is a heartbeat rate monitor integrated circuit. The wafer yield is analyzed against the process control monitoring (PCM) parameter measurement values. The SOM efficiently reduces the parameter space dimensions and helps in visualizing the different parameter relations. This makes it possible to identify the most probable PCM parameters affecting the yield. Those were found out to be NMOS transistor drain current and aluminium sheet resistance.     

Poisson process and integrated circuit yield prediction

Initial integrated circuit yield predictions were overly pessimistic because the assumption that defects were a homogeneous random population led to the logarithm of yield linearly declining with increasing chip area. In reality, the yield vs area curve is concave up, which can be successfully modeled by partitioning the wafer into several Poisson subareas of different defect densities. Previously, this partitioning was done by “eye”. Here an algorithm has been developed to do the partitioning. Good results over a wide range of yields have been obtained. For the particular data presented, the yield curves in the range of interest can be described by a negative binomial distribution, which implies the underlying defect density is governed by the gamma distribution. As previously anticipated, both led to overpredictions of the yield for large chip areas.     

混合集成电路金铝键合退化与控制研究动态

混合集成电路的两种金铝键合系统,有着不完全相同的两种退化模式。综述了相关的退化机理和控制方法的研究状况。金丝与芯片铝膜的Au/Al键合系统,是键合IMC、Kirkendall空洞导致其界面开裂失效;铝丝与厚膜金导体的Al/Au键合系统,除了界面开裂外,还存在键合根部因铝原子向IMC过度迁移而形成铝丝内部空洞导致铝丝断裂。采用铜丝代替金丝,可有效控制Au/Al键合系统的退化;采用过渡垫片或在金浆料中加入少量Pd,同时减少金导体膜厚度,可有效控制铝丝Al/Au键合系统的退化。     

Modeling of copper wire bonding process on high power LEDs

In this paper, a couple thermal mechanical transient dynamic finite element framework of copper wire bonding process on high power lighting emitting diodes (LEDs) is developed, which considers the thermal heating effects of friction and plastic deformation. The whole wire bonding process is simplified to consist of impact and ultrasonic vibration stages. Parametric studies are also carried out to examine the effects of ultrasonic vibration amplitude and bonding force on stress/strain distribution and friction thermal heating effect during wire bonding process. Different friction coefficients of interface between the free air ball (FAB) and the bond pad are taken in the simulation to examine the effects of friction on the stress and strain level of electrode structure. Modeling results show that the stress/strain distribution and temperature evolution of wire bonding system are significant influenced by the ultrasonic vibration amplitudes, bonding forces and friction coefficients. Discussion and comparison are conducted between the copper and the gold wire bonding processes on the high power LEDs by numerical simulation. The results have disclosed that higher stress/strain in the bond pad and the ohmic contact layer is induced during the copper wire bonding process. Therefore, the process parameters of copper wire bonding should be controlled carefully. This numerical simulation work may provide guidelines for the copper wire bonding process virtual window development of high power LEDs packaging.     

基于自适应模糊理论的某型无人机起飞控制方法

基于合理简化的无人机纵向模型,设计了一种自适应模糊控制器,该控制器将Takagi-Sugeno模糊系统与等效控制器相结合,以增强系统的鲁棒性.只要求预先知道系统的相对阶以及未知函数的上下界即可,不需要精确的数学模型.Lyapunov合成方法证明了跟踪误差能趋近于零且其余的控制信号均有界.最后,结合优先级按比例分配的控制分配器,给出了存在扰动情况下飞行控制系统的仿真结果,表明即使在模型部分未知的情况下,该系统仍然能够达到飞行控制的指标性能和品质要求,验证了该方法的有效性.     

Two capillary solutions for ultra-fine-pitch wire bonding and insulated wire bonding

In this article, the new challenges and requirements in wire bonding are discussed, the problems in ultra-fine-pitch wire bonding and insulated wire bonding are analyzed, and then two capillary solutions to the problems are presented. Actual bonding experiments using the new capillaries were carried out and the results were satisfactory. Compared to the standard design, a new capillary design has a larger inner chamfer, a larger chamfer diameter and a smaller chamfer angle. This new capillary design has proved to improve the ball bondability and smaller ball size control for ultra-fine pitch wire bonding. A unique surface characteristic on the capillary tip surface has also been derived. The new finishing process developed creates a new surface morphology, which has relatively deep lines with no fixed directions. Compared to the standard capillary, this capillary has less slipping between the wire and the capillary tip surface in contact, and provides better coupling effect between them and better ultrasonic energy transfer. This capillary has been used to effectively improve the bondability of the stitch bonds for insulated wire bonding.     

Silver pick up during tail formation in thermosonic wire bonding process

Cu ball bonding processes are significantly less robust than Au ball bonding processes. One reason for this are higher variations observed, e.g. in the free-air ball (FAB) formation process. There is a strong influence the tail bond process has on subsequent FAB formation. Tail tips and bond fractographs made with Cu and Au wires are investigated using scanning electron microscopy. Au and Cu wires pick up Ag material (Ag pick up) from the Ag metallization of Cu leadframe diepads during wire tail breaking. Ag pick up by Cu wire is more dominant than that by Au wire. Ultrasonic friction energy is necessary in order for Ag material pick up to occur. The impact force plays an important role for Ag pick up; less pick up is observed with a higher impact force. The hardness of the free-air ball (FAB) with Ag pick up is reduced by up to 4% compared to that of a FAB made from a tail broken at the neck of a ball bond and therefore having no Ag pick up. No significant change of FAB diameter is observed in these two cases.     

基于NiPdAu PPF框架的QFN键合工艺研究

本文首先介绍了NiPdAu PPF (Pre-platedFrame)框架的镀层结构以及键合机理。并针对QFN(Quad Flat Non-lead)封装类型,研究了基于PPF框架的键合工艺的优化,着重探讨了为增强第二焊点焊接强度所进行的工艺参数改进。     

Taurus Workbench虚拟IC芯片加工系统

介绍了被业界称之为“虚拟集成电路芯片加工厂”的TCAD集成化仿真系统Taurus Workbench（TWB)及其优化机制。     

Overview of wire bonding using copper wire or insulated wire

Wire bonding using copper or insulated wire leads to many advantages and new challenges. Research is intensively performed worldwide, leading to many new findings and solutions. This article reviews recent advances in wire bonding using copper wire or insulated wire for advanced microelectronics packaging. Journal articles, conference articles and patents published or issued recently are reviewed. The benefits and problems/challenges related to wire bonding using copper wire or insulated wire such as wire open and short tail defects, poor bondability for stitch/wedge bonds, oxidation of Cu wire, and stiff wire on weak support structures, are briefly analyzed. A number of solutions to the problems and recent findings/developments related to wire bonding using copper wire or insulated wire are discussed. With the references provided, readers may explore more deeply by reading the original articles and patent documents.     

Adaptive fuzzy neural network control for motor-toggle servomechanism

In this study, the dynamic responses of an adaptive fuzzy neural network (FNN) controlled toggle mechanism is described. The toggle mechanism is driven by a permanent magnet (PM) synchronous servo motor. First, based on the principle of computed torque, an adaptive controller is developed to control the position of a slider of the motor-toggle servomechanism. Since the selection of control gain of the adaptive controller has a significant effect on the system performance, an adaptive FNN controller is proposed to control the motor-toggle servomechanism. In the proposed adaptive FNN controller, an FNN is adopted to facilitate the adjustment of control gain on line. Moreover, simulated and experimental results due to a periodic sinusoidal command show that the dynamic behaviors of the proposed adaptive and adaptive FNN controllers are robust with regard to uncertainties.     

Advanced neural network model of plasma-driven integrated circuit process data

Plasma processes are key means to deposit or etch thin films during the manufacture of integrated circuits. An advanced model of plasma process data was constructed by applying genetic algorithm to the set of typical training factors combined with multi-parameterized gradients of neuron activation functions. The presented technique was evaluated with plasma etch data, collected during silica etching in CHF₃-CF₄ inductively coupled plasma. The etch responses measured include Al etch rate, Al selectivity over silica etch rate, silica profile angle, and DC bias. Constructed models demonstrated better predictions over conventional models for all etch responses. The improvement measured by the relative percentage error was even more than 30%. This was also demonstrated over previous models. In consequence, the presented modeling technique can be effectively applied to construct accurate prediction models with a limited set of experimental data.     

基于LTCC技术的Ku波段金丝线匹配的研究

基于低温共烧陶瓷(LTCC)技术,设计了Ku波段金丝键合线宽带匹配电路,该电路应用多节1/4波长传输线对两根金丝键合线在Ku波段进行了具有二项式响应的宽带匹配.三维电磁场仿真表明,匹配后在Ku波段的回波损耗达到-20 dB.以下,有效提高了信号的通过率.该匹配电路在LTCC基板上所占面积小、实现较为简单.     

Evaluation of wire bonding performance, process conditions, and metallurgical integrity of chip on board wire bonds

Chip on board wire bonding presents challenges to modern wire bonding technology which include smaller, closely spaced wire bond pads; bonding to soft substrates without special processing and pad construction; and diverse first bond and second bond metallurgies. These challenges are addressed by extensive bonding accuracy tests, a design of experiments approach for optimizing wire bond process parameters, reliability testing, and detailed materials characterization of the metallurgical integrity of the wire bonds. The thermo-mechanical integrity of the wire bond interconnects was evaluated by wire pull and hot storage tests. Hot storage testing allowed for detection of samples with an electrolytic gold surface finish that was too thin, and exhibited a contamination-corrosion condition of the nickel under-plating. Other samples with an excessively thick, rough textured nickel under-plating layer exhibited poor wire bond-ability. The methodology of materials analyses of the metallurgy of the wire bond interconnects is described. The paper illustrates a wire bond lift technique that is used to inspect for cratering damage and the “area-uniformity” of gold aluminum intermetallics. An improved understanding of the wire bonding process was achieved by showing the dependence of the visual appearance of the wire bonds on wire bond process parameters.     

Optimization of the Cu wire bonding process for IC assembly using Taguchi methods

The yield of IC assembly manufacturing is dependent on wire bonding. Recently, the semiconductor industry demands smaller IC designs and higher performance requirements. As such, bonding wires must be stronger, finer, and more solid. The cost of gold is continuously appreciating, and this has become a key issue in IC assembly and design. Copper wire bonding is an alternative solution to this problem. It is expected to be superior over Au wires in terms of cost, quality, and fine-pitch bonding pad design. To obtain the best wire bonding quality, we employed Taguchi methods in optimizing the Cu wire bonding process. With Cu wire bonding technology, the production yield increased from 98.5% to 99.3% and brought approximately USD 0.7 million in savings.